Added functionality to create an upload policy document

(Removed acl related code from commit)
Continued the work of @goldv to add upload policy document helpers to
the library

- Made the creation of a policy file more userfriendly.
- Added tests that actually uploads a file with a policy.
- Updated README
- Updated version
- Added Form helper that can convert policy conditions to usable
FormElement entries (which can be used to construct an html form)